Synthesis
GENERAL STEPS: Pd(dppf)Cl2 (29 mg, 0.04 mmol, 3 mol%) and tert-butyl 5-chloro-3-iodo-1H-indole-1-carboxylate (500 mg, 1.32 mmol) were added to a dry screw-capped reaction flask equipped with a septum under argon protection. Subsequently, anhydrous toluene (6.5 mL) was added and the mixture was degassed with argon for 5 minutes. Under argon atmosphere, dry triethylamine (0.7 mL) and 4,4,5,5-tetramethyl-1,3,2-dioxaborolane (0.3 mL, 2 mmol) were added sequentially. The reaction mixture was placed in an oil bath preheated to 80 °C and stirred for 3 h. The reaction progress was monitored by TLC. After completion of the reaction, the mixture was cooled to room temperature and filtered through diatomaceous earth. The filtrate was concentrated under reduced pressure and the residue was purified by fast column chromatography (eluent: hexane/ethyl acetate = 10/1) to afford the target product 1-Boc-5-chloroindole-3-boronic acid pinacol ester (418 mg, 84% yield). The product characterization data were consistent with those reported in the literature.1H NMR (500 MHz, CDCl3) δ 8.08 (d, J=8.8 Hz, 1H), 8.00 (s, 1H), 7.95 (d, J=2.1 Hz, 1H), 7.26 (dd, J=8.8,2.1 Hz, 1H), 1.65 (s, 9H), 1.38 (s, 12H).
References
[1] Bioorganic and Medicinal Chemistry, 2017, vol. 25, # 5, p. 1622 - 1629
[2] European Journal of Organic Chemistry, 2011, # 24, p. 4532 - 4535
[3] European Journal of Organic Chemistry, 2013, # 21, p. 4564 - 4569
